Content warning: just tech.
If you’re running the Oracle JDK 7 on your OS X Mavericks machine you may have noticed that the control panel doesn’t do anything. In particular, you can’t switch back and forth between enabled and disabled Java. Silent failure occurs.
It is officially a bad idea to run Java in your browser, which is why it’s disabled by default. However, sometimes it’s necessary to use the damned thing for some job-related or government nonsense. Here’s how. Disclaimer: I am just another user. This may destroy your life. It works for me.
Open a command line. and execute the following:
cd '/Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/'
sudo mv Info.plist Infoplist.bak
sudo ln -s Enabled.plist Info.plist
Close your terminal. You should now be able to use the browser plugin with Firefox and Safari. It can’t work in Chrome for other reasons.
THEN of course remember to turn it back off:
cd '/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/'
sudo rm Info.plist
sudo mv Infoplist.bak Info.plist
I hope this works for you. It did for me.